<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8" />
    <title>2.关于函数的返回值</title>
  </head>
  <body>
    <script type="text/javascript" >
      function demo(){
        return setTimeout(function(){
          return 678
        }, 1000);
      }

      let x = demo()
    </script>
  </body>
</html>